Most of my photos are being rejected. Can I please be advised why. Thank you.

After examining the photo further I noticed that several of the highlighted boats and houses are overexposed and need to be removed. I came up with this to give you an idea.

make the backround smooth and their are too darkness

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From a compositional point of view you divided the photo into two parts, sky and foreground. I would suggest having more foreground or more sky, rather than half and half.

I think you could also crop this to landscape orientation and reduce the bright whites a bit.

Open up the shadows and crop out the house on the left side.